**3.3 Requirements for compliant processed biogas**

The composition, the combustion-related characteristic data and the accompanying substances in the "processed biogas" - summarized under the term "gas properties" - are crucial for injection. In particular, these are the data described in the DVGW work sheet G 260 "gas properties", G 262 "use of regeneratively produced gases" and in the DVGW Worksheet G 685 "gas billing" and G 486 and are defined within their respective limits. Table 7 shows the principal conditioning parameters for injecting into a grid.

The methane content in biogas is not subject to any defined restriction. However methane is, according to the latest technical data, the major combustible component and thus largely determines the calorific value and hence the Wobbe index, as long as no liquid gas admixture is included. According to worksheet DVGW-G 262, the maximum permissible CO2 content is 6 Vol.-%. Since biogas consists mostly of methane and carbon dioxide,

in kWh/m³

As a basis for further considerations, data for the biogas compositions as specified in Table 6 will be used. Further accompanying substances occurring in the biogas have not been taken into account, because they vary too greatly depending on the fermented substrates and type

Components Unit Case 1 Case 2 Case 3 Case 4 CH4 Vol.-% 94 96 98 99,5 CO2 Vol.-% 5,6 3,6 1,6 0,1 N2 Vol.-% 0,3 0,3 0,3 0,3 O2 Vol.-% 0,1 0,1 0,1 0,1 Calorific value kWh/m³ 10,400 10,622 10,843 11,009 Wobbe - Index WS,n kWh/m³ 13,290 13,798 14,326 14,738

A processing level of 99.5% vol. methane is attainable and is state of the art. The N2 and O2 levels are 0.3 and 0.1 vol -% and remain constant for the calculations at these initial methane levels. The CO2 content conforms to the relevant selected methane content within the

The composition, the combustion-related characteristic data and the accompanying substances in the "processed biogas" - summarized under the term "gas properties" - are crucial for injection. In particular, these are the data described in the DVGW work sheet G 260 "gas properties", G 262 "use of regeneratively produced gases" and in the DVGW Worksheet G 685 "gas billing" and G 486 and are defined within their respective limits. Table

The methane content in biogas is not subject to any defined restriction. However methane is, according to the latest technical data, the major combustible component and thus largely determines the calorific value and hence the Wobbe index, as long as no liquid gas admixture is included. According to worksheet DVGW-G 262, the maximum permissible CO2 content is 6 Vol.-%. Since biogas consists mostly of methane and carbon dioxide,

Designation Calorific range (+/-2%)

North Sea I 11,956 – 12,444 Holland II 9,996 – 10,404 Weser Ems L Gas 9,653 – 10,047

Table 6. Examples of the composition of processed biogases

**3.3 Requirements for compliant processed biogas** 

7 shows the principal conditioning parameters for injecting into a grid.

Table 5. Calorific value ranges

of processing.

specified range.

**3.2 Data on processed biogases** 

processing to at least a minimum methane content of 94 vol -% is assumed. Together with the fractions of oxygen and nitrogen, the biogas has a maximum carbon dioxide content of 5,6 Vol.-%.


Table 7. Requirements for processed biogas

According G 260, the maximum permissible O2 volume fraction is 3% in dry networks, otherwise 0.5%. German natural gas grids are considered to be dry.

It is important to note that CO2 and O2 in combination with moisture can lead to corrosion in pipes, fittings and equipment.

In addition to the above conditions, of course the information on sulphur compounds and other impurities and accompanying substances given in G 260 is also to be noted. The data

Conditioning of Biogas for Injection into the Natural Gas Grid 379

10,0 10,5 11,0 11,5 12,0 12,5 13,0 13,5 14,0 14,5

 **LPG-Zugabe Wobbe-Index**

**HS,n in kWh/m³**

10,0 10,5 11,0 11,5 12,0 12,5 13,0 13,5 14,0 14,5

**HS,n in kWh/m³**

Fig. 3. Possible H gas mixtures by admixing LPG to an initial concentration of 96 Vol. -%

Fig. 2. Possible H gas mixtures by admixing LPG to an initial concentration of 94 Vol. -%

 **LPG Zugabe Wobbe-Index relative Dichte**

13,0

0,56 0,58 0,60 0,62 0,64 0,66 0,68 0,70 0,72 0,74

**relative Dichte**

13,5

14,0

14,5

**Wobbe - Index WS,n in kWh/m³**

**LPG - Zugabe inv Vol.-%**

**11,3**

**8,1**

15,0

15,5

16,0

**H-Gas Grenze**

16,5

13,0

0,56 0,58 0,60 0,62 0,64 0,66 0,68 0,70 0,72 0,74

**relative Dichte** 

13,5

14,0

14,5

**LPG-Zugabe in Vol.-%**

**9,4**

**12,6**

 **relative Dichte**

**Wobbe - Index WS,n in kWh/m³**

15,0

15,5

16,0

**H-Gas-Grenze**

16,5

methane

 **Methan** 

methane

**Methan-Konzentration** ϕ**CH4 in Vol.-%**

**Methan-Konzentration**

 ϕ**CH4 in Vol.-%**

 **Methan**

for the dew point temperatures lie below the requirements defined in G 260 (about 4 - 7 ° C (soil temperature at 1 m depth) at line pressure).
